The present invention relates to a valve operating device for an engine of a vehicle, particularly a valve operating device which switches a cam for opening and closing a valve.
A type of valve operating device for an engine is known, which is provided with a plurality of cams having nose parts in different shapes for each valve, and for switching opening degrees and open and close timings of intake and exhaust valves by selecting the cam for opening and closing the valves from among the plurality of cams, according to an operating state of the engine.
For example, US2011/0226205A1 discloses such a valve operating device. The valve operating device includes a camshaft comprised of a shaft and a cylindrical cam element spline-fitted onto the shaft and slidable in axial directions along the shaft. For each valve, a plurality of cams, each having a nose part in a different shape, are provided adjacent to each other in the outer circumference of the cam element. The valve operating device switches the cam for opening and closing the valve by sliding the cam element in one of the axial directions.
In this case, in the valve operating device of US2011/0226205A1, an end face cam is formed in one end face of the cam element, and a control member is provided to be able to enter into and retreat from a position adjacent in the axial directions to the end face cam and push the cam element in one of the axial directions by engaging with the end face cam in the entry. The valve operating device switches the cam by actuating the control member with an actuator.
Meanwhile, in the valve operating device of US2011/0226205A1, in order to move the cam element on the shaft in both axial directions, an end face cam is formed in both end faces of the cam element and a control member is provided for each of the end face cams on each side. Therefore, two control members are required for one cam element, and the number of components increases.
Particularly, with multi-cylinder engines, when a cam element is provided for each cylinder on a shaft of a single camshaft, two control members need to be disposed within a space on the camshaft between two cylinders for respectively moving, in the axial directions, the cam element of the cylinder on one side and the cam element of the cylinder on the other side. Thus, the distance between the two cylinders increases to secure the space and, as a result, the size of the engine increases.
Moreover, among multi-cylinder engines, in the case of a four-valve DOHC engine provided with two intake valves and two exhaust valves for each cylinder, in order to secure a space on the camshaft to dispose two control members between two cylinders, a distance between at least two intake valves or two exhaust valves has to be reduced for each cylinder, and thus, an opening area of each of the intake and exhaust valves into a combustion chamber is limited.
Further, regardless of whether an engine is a single-cylinder engine or multi-cylinder engine, when two cam elements for intake and exhaust valves are provided at a single camshaft for each cylinder, two control members are disposed in a central section of the cylinder and, in this case, the distance between the two valves becomes long and, similarly to the case described above, an opening area of each of the intake and exhaust valves into a combustion chamber is limited.